1. Field of the Invention
The present invention relates to a gas turbine exhaust passage applied to simple cycle gas turbines and combined cycle gas turbines having a bypass chimney or the like and to a damper system for same.
2. Description of the Related Art
FIG. 8 shows a conventional simple cycle gas turbine exhaust passage, and FIG. 9 shows a conventional combined cycle gas turbine exhaust passage. In FIG. 8, the exhaust passage is connected to a gas turbine body 1 through an exhaust diffuser 2 and is composed of an exhaust duct 3 provided with an internal exhaust silencer 4, and an exhaust chimney 5 connected to the exhaust duct 3. On the other hand, in FIG. 9, the exhaust passage is connected to the gas turbine body 1 through the exhaust diffuser 2 and is composed of an exhaust duct 3 provided with an internal exhaust silencer 4, and a bypass chimney 6 connected to the exhaust duct 3.
The general cross-sectional structures of the walls of the above-described conventional gas turbine exhaust passages are shown on an enlarged scale in FIGS. 8 and 9. In general, two types of cross-sectional structures are used. The enlarged cross-sectional structures shown in portion D in FIG. 8 and portion F in FIG. 9 are those used in the exhaust ducts 3 of the respective exhaust passages. In these cross-sectional structures, a heat insulating material 32 is sandwiched between an inner plate 31 and an outer plate 33. Also, the enlarged cross-sectional structures shown in portion E in FIG. 8 and portion G in FIG. 9 are those used in the exhaust passage chimney 5 or the bypass chimney 6 of the respective exhaust passages. In these cross-sectional structures, a refractory member 52 such as refractory bricks is lined on the inside of the outer plate 53. There is no gas permeability or acoustic transmissivity with either of these structures.
Also, as shown in FIG. 9, in the case of a combined cycle gas turbine exhaust passage, a boiler inlet duct 7 connected to the chimney 10 through an exhaust gas boiler 8 is connected to the exhaust duct 3. A bypass damper 9 is provided at a joint portion between the boiler inlet duct 7 and the exhaust duct 3. Also, as with the cross-sectional structure of each of the above-described walls, the bypass damper 9 has a structure with which there is no air permeability or sound transmissivity. The gas flow and the acoustic characteristics in the exhaust passage during the bypass operation are substantially the same as those of the exhaust passage shown in FIG. 8.
In the gas turbine exhaust passage having the conventional cross-sectional wall structure, pressure pulsation and high speed exhaust gas flow turbulence generated in a combustor of the gas turbine are amplified at a resonant frequency of the exhaust passage and an ultra low frequency noise in the range of 10 to 30 Hz is emitted from the opening of the chimney. As a result, ultra low frequency noise trouble occurs. Since portions other than the chimney opening are acoustically sealed due to the cross-sectional structure of the walls of the exhaust passage and the bypass damper, the damping of the sound field is small and the resonance magnification is high. Hence, such trouble occurs.